Throttle Valve Potentiometer, Checking

Checking Throttle Valve Potentiometer

Test sequence
- Connect VAG 1551 Scan Tool ((VAG 1552). Then switch ignition on and select engine control module with the "Address word" 01.

Indicated on display

Rapid data transfer HELP
Select function XX

- Press keys 0 and 8 for function "Read Measuring Value Block" and confirm entry with Q key.

Indicated on display

Read Measuring Value Block HELP
Input display group number XXX

- Press keys 0, 5 and 4 for "Display group number 54" and confirm entry with Q key.

Indicated on display: (1 to 4 Display zones)

Read Measuring Value Block 54 ->
1 2 3 4

- Read off throttle valve angle in display zone 3.
Throttle valve in start position: 0 to 6 angle degree
- Slowly open throttle valve slowly until fully open and observe angle display in display zone 3. Figure must increase uniformly overcomplete range up to a: min. 75.
- Press -> key.
- Press keys 0 and 6 for "End data transfer" function and confirm input with Q key.
- Switch ignition off.

NOTE: The displayed figure is dependent on the tolerances of the throttle valve potentiometer and does not correspond to the actual opening angle.

If the figure does not increase uniformly:
- Replace throttle valve control module -J338-.

If the display constantly shows 0 angle degree or is above 90 angle degrees:
Display Cause
0 angle degree Open circuit or short to positive
above 90 angle degree Short to Ground

Continuation of check when display 0 angle degree:







- Pull 8 pin connector off throttle valve control module.
- Bridge connector contacts 5+7 with auxiliary cables from VAG 1594 and observe display.

If display jumps above 90 angle degree:
- Press -> key.
- Press keys 0 and 6 for "End data transfer" function and confirm input with Q key.
- Switch ignition off.
- Replace throttle valve control module -J338-.

If display remains at 0 angle degree:
- Press -> key.
- Press keys 0 and 6 for "End data transfer" function and confirm input with Q key.
- Switch ignition off.
- Check voltage supply of throttle valve control module and wiring to control module.

If the voltage supply and wiring is OK:
- Replace engine control module.

Continuation of check when display is above 90 angle degree:







- Pull 8 pin connector off throttle valve control module.

If display jumps to 0 angle degree:
- Press -> key.
- Press keys 0 and 6 for "End data transfer" function and confirm input with Q key.
- Switch ignition off.
- Replace throttle valve control module -J338-.

If display remains above 90 angle degree:
- Press -> key.
- Press keys 0 and 6 for "End data transfer" function and confirm input with Q key.
- Switch ignition off.
- Check voltage supply of throttle valve control module and wiring to control module.

If the voltage supply and wiring is OK:
- Replace engine control module.

Checking voltage supply and wiring to control module







- Pull 8 pin connector off throttle valve control module.
- Connect multimeter to measure voltage at connector contacts 4+7.
- Switch ignition on.
Specification: min. 4.5 V
- Connect multimeter to measure voltage at connector contacts 3+7.
Specification: at least 9 V
- Switch ignition off.

If the specifications are not attained:







- Connect test box VAG 1598/22 to control module wiring harness.







- Check wiring for open circuit between test box and connector using wiring diagram:
Contact 1 + socket 66
Contact 2 + socket 59
Contact 3 + socket 69
Contact 4 + socket 62
Contact 5 + socket 75
Contact 7 + socket 67
Contact 8 + socket 74
Wire resistance: max. 1.5 Ohm
- Check additional wires for short to one another.
Specification: Infinite Ohm

If no wiring malfunction is detected:
- Check engine control module voltage supply. Voltage Supply For Engine Control Module (ECM), Checking